Liquid-cooled internal combustion engines used to power motorized land vehicles, e.g., passenger autos, construction machines and the like, use an engine block of the type having a multi-passage cooling "jacket." Coolant, usually a mix of water and ethylene glycol, is pumped through the jacket passages and absorbs heat resulting from engine operation. The heated coolant is delivered to a heat exchanger (often referred to as a "radiator") where it is cooled as it gives up heat to the atmosphere. Such coolant is then recirculated back to the cooling jacket.
To function most efficiently and effectively, it is required that air flow across the heat exchanger at a relatively high volumetric rate. While passenger autos are equipped with radiator fans, it is not unusual to automatically disable the fan at highway speeds; the ram-urged air through the heat exchanger is sufficient to remove heat from the coolant. And it is also noteworthy that engine rotational speed and vehicle speed over-the-road are roughly proportional to one another; a slower-running vehicle usually requires less engine cooling. Exemplary cooling systems for over-the-road vehicles are disclosed in U.S. Pat. Nos. 4,969,421 (Haner et al.); 5,046,554 (Iwasaki et al.) and 5,495,909 (Charles).
On the other hand, cooling the engine of an off-highway vehicle presents a different set of technical problems. There are at least three reasons why this is true. One is that even if the heat exchanger is mounted at the front of the vehicle, there is little ram-urged air available to remove heat from the coolant flowing through the heat exchanger--most off-highway vehicles are stationary or move at low ground speed when working. Therefore, some sort of air-moving apparatus must be relied upon to provide a sufficient volumetric flow rate of cooling air.
Another is that when working, the engine is often set to run continuously at full throttle to make available high engine horsepower. It is not unusual to run the engine of an off-highway at 2300-2700 rpm. Implement and vehicle speeds are controlled by, e.g., hydraulic valves and torque-converter-type automatic transmissions. When running at high speed, engines and cooling fans of the types commonly used in off-highway vehicles produce a good deal of noise. While quieter fans with forwardly-turned blades are known, they have not been used on off-highway vehicles, insofar as is known.
Yet another reason relates to the first. Often, the engine is mounted at the rear of the vehicle behind the operator and forward vehicle motion results in no ram-urged cooling air whatsoever.
Exemplary cooling systems for off-highway vehicles are disclosed in U.S. Pat. Nos. 3,921,603 (Bentz et al.); 4,377,203 (Ejima) and 4,815,550 (Mather et al.). The system disclosed in the Mather et al. patent seemingly presents some problems. One is that such system uses, in one embodiment, a double-bladed fan and in any event, uses two opposed inlets. Any openings in the housing around a fan provide a path for fan noise to escape and be heard by the operator and bystanders.
Another is that the double-outlet exhaust is directed to either side of the vehicle. This could present a modest hazard for persons passing near the vehicle while it is in operation.
An improved off-highway-vehicle cooling system which addresses some of the problems and shortcomings of earlier work in this field would be an important technological advance.